Q: I cannot export videos from my iPhone's iMovie

I doubt I have a solution for you, but you should at least share the text of the error message in case it means something to somebody else. It may help to close all apps and reboot the device before attempting to make the export again. If you can export to iTunes you should be able to copy off the project using the file sharing area on your device's apps page when it is connected to iTunes.

tt2

I have the same issue, it only states that an error occurred during export.

I had this issue a while back. Not sure what triggered it, but making a small adjustment to my project seemed to fix it. (In my case, I added a title on my first clip and it exported fine after that). It's some sort of bug and it appears to have been around for several versions. If you can't get it to work, you should report it to Apple here:  http://www.apple.com/feedback/imovie_ios.html